Cylinders, such as hydraulic or pneumatic cylinders, include a cylinder body and a piston/rod assembly. The cylinder body defines a bore in which a piston portion of the piston/rod assembly is located. The piston portion divides the bore into first and second variable volume fluid chambers. A rod portion of the piston/rod assembly extends from the piston portion, through at least one of the first and second chambers and out of the cylinder body. Generally, a sealing assembly is located on an end cap of the cylinder body for sealing against the rod portion as the rod portion exits the cylinder body. The rod portion of the piston/rod assembly moves with the movement of the piston/rod assembly.
The end of the rod portion of the piston/rod assembly located outside of the cylinder body often is attached to another part or structure. For attaching the end of the rod portion to another part or structure, the end of the rod portion commonly includes a mating feature. There are four common styles of the mating features for the end of the rod portion. The four common styles include a small male threaded end, a larger male threaded end, a female threaded end, and a flanged coupler. The flanged coupler style includes an annular groove that is machined into the cylindrical outer surface of the rod portion at a location near the end. The groove receives a snap ring that functions to connect the end of the rod portion to a female member of another part having an internal groove. The flanged coupler style is common in industries such as, for example, the die casting industry.
It is not uncommon for the mating feature of the rod portion to break, particularly when the mating feature is of the small male threaded end or the flanged coupler style. Stresses often concentrate at reduced diameter sections of the end of the rod portion. For example, in the flanged coupler style, stresses often concentrate at a corner of base and a radial shoulder that define the annular groove. The flanged coupler commonly breaks when the cylinder is pulling a load and the snap ring is concentrating the stresses of the load against the radial shoulder. When the mating feature of the rod portion breaks, the entire piston/rod assembly of the cylinder must be replaced. Replacing the piston/rod assembly commonly requires removal and complete disassembly of the cylinder. Such a repair is time consuming and is very costly. A cylinder having a design that would reduce these costly repairs is desirable.